The concept of using biomass-derived materials to produce other useful products has been explored since man first used plant materials and animal fur to make clothing and tools. Biomass derived materials have also been used for centuries as adhesives, solvents, lighting materials, fuels, inks/paints/coatings, colorants, perfumes and medicines. Recently, people have begun to explore the possibility of using “refined biomass” as starting materials for chemical conversions leading to novel high value-in-use products. Over the past two decades, the cost of renewable biomass materials has decreased to a point where many are competitive with those derived from petroleum. In addition, many materials that cannot be produced simply from petroleum feedstocks are potentially available from biomass or refined biomass. Many of these unique, highly functionalized, molecules would be expected to yield products unlike any produced by current chemical processes. “Refined biomass” is purified chemical compounds derived from the first or second round of plant biomass processing. Examples of such materials include cellulose, sucrose, glucose, fructose, sorbitol, erythritol, and various vegetable oils.
A particularly useful class of refined biomass is that of aldaric acids. Aldaric acids, also known as saccharic acids, are diacids derived from naturally occurring sugars. When aldoses are exposed to strong oxidizing agents, such as nitric acid, both the aldehydic carbon atom and the carbon bearing the primary hydroxyl group are oxidized to carboxyl groups. An attractive feature of these aldaric acids includes the use of very inexpensive sugar based feedstocks, which provide low raw material costs and ultimately could provide low polymer costs if the proper oxidation processes are found. Also, the high functional density of these aldaric acids provide unique, high value opportunities, which are completely unattainable at a reasonable cost from petroleum based feed stocks.
Hydrogels (hydrated gel) are polymers that contain water-swellable, three-dimensional networks of macromolecules held together by covalent or noncovalent (e.g., ionic or hydrogen bonded) crosslinks. Upon placement in an aqueous environment, these networks swell to the extent allowed by the degree of crosslinking. They are used in many fields such as medical applications, personal care formulations, coatings, and surfactants.
U.S. Pat. No. 5,496,545 discloses crosslinked polyallylamine and polyethyleneimine. The crosslinking agents disclosed include epichlorohydrin, diepoxides, diisocyanates, α,ω-dihaloalkanes, diacrylates, bisacrylamides, succinyl chloride, and dimethyl succinate. Applicants have invented a process to prepare new crosslinked polymers that can function as hydrogels, using crosslinking moieties that could be derived from biomass sources.